TinyBuddy: A host board for the ATTINY84

IMG_1902bI’m going to be making a large 7-segment display clock later, and I needed a control board for it.  Rather than purpose build something, I set out to make a generalized board I could reuse with various projects based on the Arduino-compatrible ATtiny84 microcontroller.

The result is the TinyBuddy: a general host PCB for the ATtiny84. Features two buttons (plus reset), a power LED, activity LED, 16MHz crystal for accurate timekeeping, and USB or DC barrel jack for power. The pins are one-to-one correlated to the pins of the bare chip, so it’s a drop in replacement on a breadboard.  While the prototype (pictured here) used micro-USB for power, I designed a second revision that uses entirely through-hole parts for easy construction. It can be fabricated for about $7 through OSH Park!

You can find the Eagle design files for it on github, or order it directly from OSH Park (Rev1 with micro USB, Rev2 with barrel jack).

IMG_1900bSome build history after the break. 

Here’s the OSH park mockup of rev1, shown fully built above:


Once I built it, I noticed a few problems:

  • Ergonomic problem: instinct is to use it upside down
  • Surface mount micro USB sucks to solder
  • Programming ribbon cable presses up against reset button
  • Pin silkscreens often cut off
  • Labels of S7 and S8 reversed (duh!)

Revision 2 fixes this by doing the following:

  • Reoriented text and components to be used with chip facing away
  • Switched to DC barrel connector for power
  • Rearranged components to separate programming port, arranged things better
  • Design now uses entirely through-hole components
  • Tweaked pin silk screens
  • Fixed button labels

Here’s a mockup pic of rev 2, which I have on order now:

rev2-topHopefully it fixes the issues above.  In any case, rev1 is certainly good enough to run a clock!

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